Concrete double Tee beams such as in parking garages are typically supported at the ends by concrete walls having preformed structures such as pockets or ledges within the concrete walls, or corbels protruding from the walls. Concrete corbels tend to deteriorate of crumble over time, due to salt, water and ice, and can become structurally deficient. Replacing deteriorated concrete corbels can be difficult and expensive. Another drawback of such prior art preformed concrete structures is that typically the size of the pocket, ledge or corbel is not easily altered on-site during building.